USB Hub Class Decoder
A Hub is a USB device that provides the electrical interface between USB devices and the host system. Hubs provide additional USB attachment points allowing many USB devices to be connected to a single USB port on the host computer or another hub. USB Hubs are responsible for detecting connection and disconnection events on their downstream ports and reporting this information to the host. Hubs are capable of supporting any speed or type of USB peripheral that is connected on their downstream ports. USB 2.0 hub provides support for high-speed, full-speed, and low-speed USB peripherals.
Universal Serial Bus Specification defines Hub class-specific descriptors and requests. USBlyzer includes fully comprehensive USB Hub Class Decoder that helps you easily visualize various USB Hub class-specific requests. USB Hub Descriptor is also decoded.
Hub Class-Specific Protocols
All Hub Class, SubClass and Protocols below are supported:
|09h - Hub
||00h - Full-speed Hub
01h - Hi-speed Hub with single TT
02h - Hi-speed Hub with multiple TTs
Hub Class-Specific Descriptors
Hub class device uses class-specific descriptor which defines a hub device and the ports on that hub. USBlyzer decodes and displays Hub class-specific descriptor.
Below is an example of decoding hi-speed Hub and super-speed Hub Descriptors.
Hub Class-Specific Requests
The hub class defines a number of class-specific requests to which hubs respond.
All USB Hub Class requests below are supported:
Get Hub Status (GET_STATUS)
Get Port Status (GET_STATUS)
Clear Hub Feature (CLEAR_FEATURE)
Clear Port Feature (CLEAR_FEATURE)
Get Bus State (GET_STATE) obsolete since USB 2.0
Set Hub Feature (SET_FEATURE)
Set Port Feature (SET_FEATURE)
Get Hub Descriptor (GET_DESCRIPTOR)
Set Hub Descriptor (SET_DESCRIPTOR)
Clear TT Buffer (CLEAR_TT_BUFFER)
Reset TT (RESET_TT)
Get TT State (GET_TT_STATE)
Stop TT (STOP_TT)
For complete description of USB Hub Class requests, refer to Universal Serial Bus Specification.
Below are examples of decoding Get Port Status and Get Hub Descriptor requests.